Western University Unsealed Nuclear Substance Contamination Monitoring Record

Transcription

1 Western University Unsealed Contamination Monitoring Record Permit Holder: Room number: A. Indirect Monitoring (Wipe test using liquid scintillation counter or NaI counter) Counter Type: Make Model Contamination limit is 3 Bq/cm 2 or net count rate is 900 cpm (assuming 10% collection efficiency, 100 cm 2 wiped area and 50% detector efficiency (as a conservative approach for most unsealed nuclear substances used). If detector efficiency is less than 50% then net count rate in cpm equal to 3 Bq/cm 2 is: Record results in the table below accordingly and keep the print out from the counter in the binder. B. Direct Monitoring (Using Western calibrated contamination meter(s) for only P-32 and/or I-125) Make and Model Meter(s) : Net count rate in cpm or cps equal to 3 Bq/cm2 for P-32 (from the calibration sticker) Net count rate in cpm or cps equal to 3 Bq/cm2 for I-125 (from the calibration sticker) Direct Monitoring can be used for weekly documented contamination monitoring if radioactive work only involved P-32 and/or I-125 during that week. Record results in the table below accordingly. Note: If no radioactive work done for any specific week then contamination monitoring is not required. Indicate all non-radioactive work weeks such as ANo Radioactive Work@ in the table below accordingly. DO NOT LEAVE ANY WEEK BLANK Numbered areas to be monitored indicated on the room diagram Year Substanc e 1 Wk Jan 2 Wk Jan 3 Wk Jan 4 Wk Jan 5 Wk Jan 1 Wk Feb

2 2 Wk Feb 3 Wk Feb 4 Wk Feb 5 Wk Feb 1 Wk Mar 2 Wk Mar 3 Wk Mar 4 Wk Mar 5 Wk Mar 1 Wk Apr 2 Wk Apr 3 Wk Apr 4 Wk Apr 5 Wk Apr 1Wk May 2 Wk May 3 Wk May 4 Wk May

3 5 Wk May 1 Wk June 2 Wk Jun 3 Wk Jun 4 Wk Jun 5 Wk Jun 1 Wk Jul 2 Wk Jul 3 Wk Jul 4 Wk Jul 5 Wk Jul 1 Wk Aug 2 Wk Aug 3 Wk Aug 4 Wk Aug 5 Wk Aug 1 Wk Sep 2 Wk Sep

4 3 Wk Sep 4 Wk Sep 5 Wk Sep 1 Wk Oct 2 Wk Oct 3 Wk Oct 4 Wk Oct 5 Wk Oct 1 Wk Nov 2 Wk Nov 3 Wk Nov 4 Wk Nov 5 Wk Nov 1 Wk Dec 2 Wk Dec 3 Wk Dec 4 Wk Dec 5 Wk Dec

5 CONTAMINATION LEVEL (Bq/cm2) = S - B E x A x T x F Where: S = Sample count rate (cpm or cps) B = count rate (cpm or cps) E = Detector efficiency (e.g. if 50% efficiency, E = 0.50) A = Area wiped (100 cm 2 ) or detector area in cm 2 T = 60 sec/min if count rate in cpm T = 1 if count rate in cps F = 0.1 (e.g. 10%) is collection factor for area wiped (indirect monitoring or wipe test) Net count rate (cpm or cps) = Sample count rate (cpm or cps) count rate (cpm or cps) Detector efficiency = Net count rate (cpm) /Known activity (dpm) 1 microcurie (µci) = 2.2 x 10 6 disintegrations per minute (dpm) Detector efficiency = Net count rate (cps)/known activity (dps) 1 Becquerel (Bq) = 1 disintegration per second (dps) 1 microcurie (µci) = 37 kilobecquerel (kbq) = becquerel (Bq) Non-fixed contamination in all areas, rooms or enclosures where unsealed nuclear substances are used or stored does not exceed 3 Bq/cm 2. Problem: You have taken a swipe for unsealed H-3 and S-35 contamination in your designated radiation room. The liquid scintillation counter print out shows a sample count rate 940 cpm for the swipe the fume hood in 100 cm 2. The minimum detector efficiency is 50% and the background count rate is 40 cpm. What is the contamination level in Bq/cm 2? Solution: Contamination level (Bq/cm 2 ) = 940 cpm - 40 cpm 0.5 x 100 cm 2 x 60 sec/min x 0.1 Therefore, the contamination level is 3.0 Bq/cm 2. Also, if you know the contamination limit in Bq/cm 2 and the counter print out shows in cpm then you can calculate a net count rate in cpm equal to the known contamination limit using the contamination level formula above. Problem: The contamination limit is 3 Bq/cm 2, 50% detector efficiency (as a conservative approach for most unsealed nuclear substances used), 100 cm 2 wiped area and 10% collection efficiency. What is the net count rate in cpm equal to 3 Bq/cm 2? Solution: Net count rate (cpm) = 3 Bq/cm 2 x 0.5 x 100 cm 2 x 60 sec/min x 0.1 Therefore, the net count rate equal to 3 Bq/cm 2 is 900 cpm.